Minimally invasive interbody fusion

ABSTRACT

Methods and apparatus are disclosed for distracting tissue. The devices and methods may include insertion of first and second elongated members into the space between two tissue layers, with an augmenting elongated member at least partially inserted therebetween to form a distraction device between the tissues to be distracted. At least one of the first and second elongated members may be formed of a flexible core member with a plurality of rigid veneer members spaced along the length of the core member. At least one of the elongated members may include a shaping member that automatically moves from a generally linear configuration to a generally less linear configuration. A deployment catheter may include a deformable distal end to allow augmentation of the tissue distraction device during implantation. An injection aid may be provided for introducing a filler material into an interior defined by a deployed tissue distraction device.

RELATED APPLICATIONS

This application is a U.S. national stage application of PCT PatentApplication Serial No. PCT/US2019/015386, filed Jan. 28, 2019, whichclaims the benefit of and priority of U.S. Provisional PatentApplication Ser. No. 62/623,025, filed Jan. 29, 2018, and U.S.Provisional Patent Application Ser. No. 62/718,570, filed Aug. 14, 2018,the contents of all of which are incorporated by reference herein.

DESCRIPTION Technical Field

The present disclosure generally relates to apparatus and methodsemployed in minimally invasive surgical procedures and more particularlyto various aspects of apparatus and methods for separating and/orsupporting tissue layers, especially in the disc space of the spine.

Background

A variety of physical conditions involve two tissue surfaces that, fordiagnosis or treatment of the condition, need to be separated ordistracted or maintained in a separated condition from one another andthen supported in a spaced-apart relationship. Such separation ordistraction may be to gain exposure to selected tissue structures, toapply a therapeutic pressure to selected tissues, to return orreposition tissue structures to a more normal or original anatomicposition and form, to deliver a drug or growth factor, to alter,influence or deter further growth of select tissues or to carry outother diagnostic or therapeutic procedures. Depending on the conditionbeing treated, the tissue surfaces may be opposed or contiguous and maybe bone, skin, soft tissue, or a combination thereof.

One location of the body where tissue separation is useful as acorrective treatment is in the spinal column. Developmentalirregularities, trauma, tumors, stress and degenerative wear can causedefects in the spinal column for which surgical intervention isnecessary. Some of the more common defects of the spinal column includevertebral compression fractures, degeneration or disruption of anintervertebral disc and intervertebral disc herniation. These and otherpathologies of the spine are often treated with implants that canrestore vertebral column height, immobilize or fuse adjacent vertebralbones, or function to provide flexibility and restore natural movementof the spinal column. Accordingly, different defects in the spinalcolumn require different types of treatment, and the location andanatomy of the spine that requires corrective surgical proceduresdetermines whether an immobilizing implantable device or a flexibleimplantable device is used for such treatment.

In a typical spinal corrective procedure involving distraction of tissuelayers, damaged spinal tissue is removed or relocated prior todistraction. After the damaged tissue has been removed or relocated,adjacent spinal tissue layers, such as adjacent bone structures, arethen distracted to separate and restore the proper distance between theadjacent tissue layers. Once the tissue layers have been separated bythe proper distance, an immobilizing or flexible device, depending onthe desired treatment, is implanted between the tissue layers. In thepast, the implantable treatment devices have been relatively largecage-like devices that require invasive surgical techniques, whichrequire relative large incisions into the human spine.

Such invasive surgical techniques often disrupt and disturb tissuesurrounding the surgical site to the detriment of the patient, soimplantable treatment devices and methods that utilize minimallyinvasive procedures may be preferable. Minimally invasive methods anddevices may be particularly needed in the area of intervertebral or disctreatment. The intervertebral disc is divided into two distinct regions:the nucleus pulposus and the annulus fibrosus. The nucleus lies at thecenter of the disc and is surrounded and contained by the annulus. Theannulus contains collagen fibers that form concentric lamellae thatsurround the nucleus and insert into the endplates of the adjacentvertebral bodies to form a reinforced structure. Cartilaginous endplatesare located at the interface between the disc and the adjacent vertebralbodies.

The intervertebral disc is the largest avascular structure in the body.The cells of the disc receive nutrients and expel waste by diffusionthrough the adjacent vascularized endplates. The hygroscopic nature ofthe proteoglycan matrix secreted by cells of the nucleus operates togenerate high intra-nuclear pressure. As the water content in the discincreases, the intra-nuclear pressure increases and the nucleus swellsto increase the height of the disc. This swelling places the fibers ofthe annulus in tension. A normal disc has a height of about 10-15 mm.

There are many causes of disruption or degeneration of theintervertebral disc that can be generally categorized as mechanical,genetic, and biochemical. Mechanical damage includes herniation in whicha portion of the nucleus pulposus projects through a fissure or tear inthe annulus fibrosus. Genetic and biochemical causes can result inchanges in the extracellular matrix pattern of the disc and a decreasein biosynthesis of extracellular matrix components by the cells of thedisc. Degeneration is a progressive process that usually begins with adecrease in the ability of the extracellular matrix in the centralnucleus pulposus to bind water due to reduced proteoglycan content. Witha loss of water content, the nucleus becomes desiccated resulting in adecrease in internal disc hydraulic is pressure, and ultimately to aloss of disc height. This loss of disc height can cause the annulus tobuckle with non-tensile loading and the annular lamellae to delaminate,resulting in annular fissures. Herniation may then occur as ruptureleads to protrusion of the nucleus.

Proper disc height is necessary to ensure proper functionality of theintervertebral disc and spinal column. The disc serves severalfunctions, although its primary function is to facilitate mobility ofthe spine. In addition, the disc provides for load bearing, loadtransfer, and shock absorption between vertebral levels. The weight ofthe person generates a compressive load on the discs, but this load isnot uniform during typical bending movements. During forward flexion,the posterior annular fibers are stretched while the anterior fibers arecompressed. In addition, a translocation of the nucleus occurs as thecenter of gravity of the nucleus shifts away from the center and towardsthe extended side.

Changes in disc height can have both local and global effects. Decreaseddisc height results in increased pressure in the nucleus, which can leadto a decrease in cell matrix synthesis and an increase in cell necrosisand apoptosis. In addition, increases in intra-discal pressure create anunfavorable environment for fluid transfer into the disc, which cancause a further decrease in disc height.

Decreased disc height also results in significant changes in the globalmechanical stability of the spine. With decreasing height of the disc,the facet joints bear increasing loads and may undergo hypertrophy anddegeneration, and may even act as a source of pain over time. Decreasedstiffness of the spinal column and increased range of motion resultingfrom loss of disc height can lead to further instability of the spine,as well as back pain.

Radicular pain may result from a decrease in foraminal volume caused bydecreased disc height. Specifically, as disc height decreases, thevolume of the foraminal canal, through which the spinal nerve rootspass, decreases. This decrease may lead to spinal nerve impingement,with associated radiating pain and dysfunction.

Finally, adjacent segment loading increases as the disc height decreasesat a given level. The discs that must bear additional loading are nowsusceptible to accelerated degeneration and compromise, which mayeventually propagate along the destabilized spinal column.

In spite of all of these detriments that accompany decreases in discheight, where the change in disc height is gradual many of the illeffects may be “tolerable” to the spine and patient and may allow timefor the spinal system to adapt to the gradual changes. However, thesudden decrease in disc volume caused by the surgical removal of thedisc or disc nucleus may increase the local and global problems notedabove.

Many disc defects are treated through a surgical procedure, such as adiscectomy in which the nucleus pulposus material is removed. During atotal discectomy, a substantial amount (and usually all) of the volumeof the nucleus pulposus is removed and immediate loss of disc height andvolume can result. Even with a partial discectomy, loss of disc heightcan ensue. Discectomy alone is the most common spinal surgicaltreatment, frequently used to treat radicular pain resulting from nerveimpingement by disc bulge or disc fragments contacting the spinal neuralstructures.

The discectomy may be followed by an implant procedure in which aprosthesis is introduced into the cavity left in the disc space when thenucleus material is removed. Thus far, the most common prosthesis is amechanical device or a “cage” that is sized to restore the proper discheight and is configured for fixation between adjacent vertebrae. Thesemechanical solutions take on a variety of forms, including solidkidney-shaped implants, hollow blocks filled with bone growth material,push-in implants and threaded cylindrical cages.

A challenge in the use of a posterior procedure to install spinalprosthesis devices is that a device large enough to contact the endplates and expand the space between the end plates of the same oradjacent vertebra must be inserted through a limited space. In the caseof procedures to increasing intervertebral spacing, the difficulties arefurther increased by the presence of posterior osteophytes, which maycause “fish mouthing” or concavity of the posterior end plates andresult in very limited access to the disc. A further challenge indegenerative disc spaces is the tendency of the disc space to assume alenticular shape, which requires a relatively larger implant than oftenis easily introduced without causing trauma to the nerve roots. The sizeof rigid devices that may safely be introduced into the disc space isthereby limited.

While cages of the prior art have been generally successful in promotingfusion and approximating proper disc height, typically these cages havebeen inserted from the posterior approach, and are therefore limited insize by the interval between the nerve roots. Further, it is generallydifficult to implant from the posterior approach a cage that accountsfor the natural lordotic curve of the lumber spine.

It is desirable to reduce potential trauma to the nerve roots and yetstill allow restoration or maintenance of disc space height inprocedures involving vertebrae fusion devices and disc replacement,containment of the nucleus of the disc, or prevention of herniation ofthe nucleus of the disc. In general, minimally invasive surgicaltechniques reduce surgical trauma, blood loss, and pain. However,despite the use of minimally invasive techniques, the implantation ofcage devices for treating the spine typically involves nerve rootretraction, an inherently high risk procedure. It is therefore desirableto reduce the degree of invasiveness of the surgical procedures requiredto implant the device, which may also serve to permit reduction in thepain, trauma, and blood loss, as well as the avoidance and/or reductionof the nerve root retraction.

In minimally invasive procedures, to monitor placement, it is usefulthat implant devices inserted into spinal tissue be detectable usingfluoroscopic imaging systems. However if a device is visible using X-raytechnology, then the device can interfere with the detection andmonitoring of spinal tissues, such as bone growing into the disc spaceafter a vertebral fusion procedure. Additional advances would also beuseful in this area.

SUMMARY

There are several aspects of the present subject matter which may beembodied separately or together in the devices, systems, and/or methodsdescribed and claimed below. These aspects may be employed alone or incombination with other aspects of the subject matter described herein,and the description of these aspects together is not intended topreclude the use of these aspects separately or the claiming of suchaspects separately or in different combinations as set forth in theclaims appended hereto.

In one aspect, a tissue distraction device includes at least oneelongated member, with a shaping member being removably associated withthe at least one elongated member. The at least one elongated member andthe shaping member are configured to change from a generally linearconfiguration to a generally less linear configuration, with the shapingmember being configured to automatically move from the generally linearconfiguration to the generally less linear configuration. Automaticmovement of the shaping member from the generally linear configurationto the generally less linear configuration causes movement of the atleast one elongated member from the generally linear configuration tothe generally less linear configuration.

In another aspect, a tissue distraction device includes at least oneelongated member comprised of an elongated internal core member and aplurality of veneer members at least partially surrounding the internalcore member and spaced along the length of the internal core member. Theinternal core member is sufficiently flexible to change between agenerally linear configuration and a generally less linearconfiguration, while the plurality of veneer members are substantiallyformed of a generally rigid material.

In yet another aspect, a tissue distraction system includes a tissuedistraction device and an injection aid. The tissue distraction deviceis configured to be positioned between tissue layers, includes anelongated guide member, and defines a window into its interior. Theinjection aid includes a follower member and a funnel member, with thefunnel member defining a lumen and extending between a proximal endconfigured to accommodate at least a portion of an injector device and adistal end. The follower member is associable with the guide member toalign the distal end of the funnel member with the window of the tissuedistraction device and to allow movement of the injection aid along atleast a portion of the length of the guide member to position the distalend of the funnel member adjacent to the window, at least partiallyinside of the window, or in the interior of the tissue distractiondevice via the window for introduction of a filler material into theinterior of the tissue distraction device.

In another aspect, a tissue distraction system includes a tissuedistraction device configured to be positioned between tissue layers.The system also includes a deployment cannula extending between proximaland distal ends and configured for introduction of the tissuedistraction device between the tissue layers. The tissue distractiondevice has a dimensional aspect in a direction extending between thetissue layers, with the dimensional aspect of at least a portion of thetissue distraction device being configured to increase while the tissuedistraction device is at least partially positioned at the distal end ofthe deployment cannula. At least a portion of the distal end of thedeployment cannula is configured to deform to accommodate the increaseof the dimensional aspect of the tissue distraction device while thetissue distraction device is at least partially positioned at the distalend of the deployment cannula.

In yet another aspect, a method is provided for manufacturing a tissuedistraction device. The method includes forming a lower portion of atleast one veneer member. An intermediate layer is formed onto the lowerportion so as to define a cavity. At least a portion of an elongatedinternal core member is inserted into the cavity. An upper portion isformed onto the intermediate portion so as to enclose the internal coremember within the cavity. The veneer member is generally rigid, whilethe internal core member is configured to change from a generally linearconfiguration to a generally less linear configuration.

In another aspect, a method is provided for manufacturing a tissuedistraction device. The method includes forming a single body piecedefining a plurality of generally rigid body elements each connected toan adjacent body element by at least one frangible bridge. The singlebody piece is associated to a generally flexible internal core member,which is moved from a generally linear configuration to a generally lesslinear configuration to break the bridges and separate each body elementfrom the adjacent body element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a distraction device according toan aspect of the present disclosure, in a generally less linearconfiguration;

FIG. 2 is a top plan view of the distraction device of FIG. 1 ;

FIGS. 3 and 4 are top perspective views of an upper elongated member ofthe distraction device of FIG. 1 in a generally linear configuration,with FIG. 4 showing interior elements of the upper elongated member;

FIG. 5 is a cross-sectional view of the upper elongated member of FIGS.3 and 4 ;

FIGS. 5A-5D illustrate an exemplary method for manufacturing the upperelongated member of FIGS. 3 and 4 ;

FIGS. 6A and 6B are top perspective views of an alternative embodimentof an upper elongated member in a generally linear configuration, withFIG. 6A showing interior elements of the upper elongated member;

FIG. 7 is an exploded view of the upper elongated member of FIGS. 6A and6B;

FIG. 8 is a top plan view of a shaping member of the upper elongatedmember of FIGS. 6A-7 , in a generally less linear configuration;

FIG. 9 is a bottom plan view of a lower elongated member of thedistraction device of FIG. 1 , in a generally less linear configuration;

FIG. 10 is a top plan view of the lower elongated member of FIG. 9 , inanother generally less linear configuration;

FIGS. 11 and 12A are end perspective views of the distraction device ofFIG. 1 , with FIG. 12A showing interior elements of the distractiondevice;

FIG. 12B is a cross-sectional view of the distraction device of FIGS. 11and 12A;

FIG. 13 is an end perspective view of an alternative embodiment of thedistraction device of FIGS. 11 and 12A, showing interior elements of thedistraction device;

FIG. 14 is an end perspective view of another alternative embodiment ofthe distraction device of FIGS. 11 and 12A, showing interior elements ofthe distraction device;

FIG. 15 is an exploded view of an upper elongated member of anotheralternative embodiment of a distraction device according to an aspect ofthe present disclosure;

FIG. 16 is a side elevational view of a single body piece of the upperelongated member of FIG. 15 ;

FIG. 17 is a bottom plan view of the single body piece of the upperelongated member of FIG. 15 ;

FIG. 18 is a perspective view of the components of a distraction deviceincorporating the upper elongated member of FIG. 15 ;

FIG. 19 is a perspective view of the distraction device of claim 18, inan assembled condition;

FIG. 20 is bottom perspective view of the distraction device of FIG. 1 ,with an associated guide member;

FIG. 21 is a bottom perspective view of the distraction device of FIG.20 , showing a deployment device being moved away from the distractiondevice, along the guide member;

FIG. 22 is a bottom perspective view of the distraction device of FIG.20 , showing an injection aid being moved toward the distraction device,along the guide member;

FIG. 23 is a bottom perspective view of the distraction device andinjection aid of FIG. 22 , with an injector device received by theinjection aid;

FIG. 24 is a bottom perspective view of the distraction device and guidemember of FIG. 20 , with a handle member associated with the guidemember for removal of the guide member from the distraction device;

FIG. 25 is a bottom perspective view of the distraction device of FIG.24 , with the guide member removed therefrom;

FIG. 26 is a perspective view of the deployment device of FIG. 21 ;

FIG. 27 is a perspective view of a cannula of the deployment device ofFIG. 26 , with components of a distraction device positioned therein;

FIGS. 28 and 29 are perspectives view of the cannula of FIG. 27 , withcomponents of the distraction device partially positioned outside of thecannula;

FIG. 30 is a perspective view of an alternative deployment cannula,showing a distraction device in a generally less linear configuration;

FIG. 31 is a perspective view of the cannula and distraction device ofFIG. 30 , showing the distraction device in a partially augmentedcondition; and

FIG. 32 is a perspective view of the cannula and distraction device ofFIG. 31 , showing the distraction device in a fully augmented condition.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The embodiments disclosed herein are for the purpose of providing anexemplary description of the present subject matter. They are, however,only exemplary, and the present subject matter may be embodied invarious forms. Therefore, specific details disclosed herein are not tobe interpreted as limiting the subject matter as defined in theaccompanying claims.

The devices and methods of the present disclosure provide multiplefeatures of distraction devices, distraction device support structures,and deployment systems that can be used to actively separate tissuelayers by engaging them and forcing them apart, or to support theseparation of tissue layers separated by the distraction device itselfor by other devices or processes or a combination of these.

As used herein, the phrases “distraction device” and “support structure”are intended to have a general meaning and are not limited to devicesthat only actively separate tissue layers, only support tissue layers oronly both actively separate and support tissue layers. For example, adistraction device or support structure in general can be used toactively separate layers of tissue and then be removed after suchseparation, or a distraction device or support structure could be usedto support layers of tissue that have been previously separated by adifferent device. Alternatively, a distraction device or supportstructure can be used to actively separate the layers of tissue andremain in place to support the layers of tissue in order to maintainsuch separation. Unless more specifically set forth in the claims, asused herein, the phrases “distraction device” and “support structure”encompass any and all of these. In addition, it should be noted that thereferences to “first” and “second” members or devices are forconvenience in the written description. They may be combined to providea single distraction assembly or structure of selected distractionheight, and the assembly is not limited to any particular number of“devices” or “members.” In keeping with the broader aspects of thepresent disclosure, the specific number of “devices” or “members” can bevaried according to the intended usage or design considerations.

It should also be understood that various embodiments of the devices,systems, and methods of the present disclosure are illustrated forpurposes of explanation in vertebral fusion procedures and/orreplacement of removed discs. However, in its broader aspects, thevarious features of the present disclosure are not limited to theseparticular applications and may be used in connection with other tissuelayers, such as soft tissue layers, although it has particular utilityand benefit in treatment of vertebral conditions within intervertebraldiscs or disc spaces.

One embodiment of a distraction device or support structure or implantis shown in FIGS. 1 and 2 . The distraction device shown in FIGS. 1 and2 is comprised of a first or upper elongated member 1, a second or lowerelongated member 2, and an augmenting elongated member 3. The augmentingelongated member 3 cooperatively interacts with the first and secondelongated members 1 and 2 to increase a dimensional aspect of thedistraction device or support structure. The distraction device ispreferably comprised of elongated members made of biocompatiblematerials (including metals and polymers) that are suitable forlong-term implantation into human tissue where treatment is needed. Thebiocompatible materials may, for example, be calcium phosphate,tricalcium phosphate, hydroxyapatite, polyetheretherketone (PEEK),nylon, titanium, Nitinol (NiTi) or any other suitable biocompatiblematerial. Suitable biocompatible material may also include PEEK withcarbon fibers, polyethylenes of low, medium, and/or high densities, aswell as nylons and blends of materials that contain nylons. It is alsowithin the scope of the present disclosure for the elongated members tobe at least partially comprised of one or more bioabsorbable materials,such as polyglycolic acid (PGA) or poly-L lactic acid (PLLA), forexample. To the extent not contradicted by the present disclosure,elongated members according to the present disclosure may bemanufactured, configured, and function generally according to thedisclosures of U.S. Pat. Nos. 8,454,617 and 9,480,574, both of which arehereby incorporated herein by reference.

According to one aspect of the present disclosure, the first and/orsecond elongated members 1 and 2 are provided with a hybrid or compositestructure, rather than a unitary structure. For example, FIGS. 3-5 showthe configuration of an exemplary embodiment of the first elongatedmember 1, with the understanding that the second elongated member 2 maybe a mirror image of the first elongated member 1 or may be differentlyconfigured. In the illustrated embodiment, the first elongated member 1is formed of an elongated internal core member 4 and a plurality ofouter skin or veneer elements or members 5, which at least partiallysurround the internal core member 4 (as best shown in FIG. 5 ) and whichare spaced along the length of the internal core member 4.

Preferably, the elongated members which form the distraction device areconfigured to change (e.g., by flexing or bending) between a generallylinear configuration for insertion into tissue or between tissue layers(FIGS. 3 and 4 ) and generally less linear configurations when deployedbetween tissue layers (FIGS. 1 and 2 ) to define the tissue distractiondevice. While FIGS. 1 and 2 show the elongated members in a generallyannular configuration, it should be understood that in changing from thegenerally linear configuration to the generally annular or closed loopconfiguration of FIGS. 1 and 2 , the elongated members pass throughintermediate, generally less linear configurations (see FIGS. 9 and 10 ,for example), which are more arcuate and less linear than the insertionconfiguration of FIGS. 3 and 4 , but less annular than the fullydeployed configuration of FIGS. 1 and 2 . As used herein, the term“annular” is not limited to substantially circular distraction devicesand elongated members, but may include other closed shapes, such asovals and rectangles, or substantially closed versions of such shapes.

To allow a hybrid elongated member (of the type shown in FIGS. 3 and 4 )to so change in configuration, the internal core member 4 is preferablyformed of a flexible material, such as PEEK or another polymer, with theinternal core member 4 being manufactured using any of a number ofsuitable techniques, including machining or milling techniques. Millingcan include cutting an internal core member 4 (or the body of anon-hybrid elongated member, such as the augmenting elongated member 3)from solid blocks or rods of PEEK or other suitable material. Aninternal core member 4 (or body of a non-hybrid elongated member) mayalso be manufactured using molding or extrusion techniques. In addition,the internal core members 4 (or bodies or non-hybrid elongated members)of the present disclosure may be manufactured with electrical dischargemachining processes and by rapid prototyping methods including fuseddeposition modeling (FDI) and stereo lithography (SLA) techniques.

In contrast to the internal core member 4, the outer veneer members 5may be formed of a generally rigid material, such as a metallicmaterial. In one embodiment, the outer veneer members 5 are formed of atitanium material, which has excellent biocompatibility with humantissue, particularly when at least a portion of an outer surface of theouter veneer members 5 (preferably a portion oriented to engage a tissuelayer) is formed so as to have a rough, porous surface for improvedbiological fixation. Regardless of the material composition andparticular configuration of the outer veneer members 5, they may beformed by any of a number of suitable approaches, including a 3Dprinting approach.

According to an exemplary approach to associating the internal coremember 4 to the veneer members 5, one or more of the veneer members 5may be partially formed, followed by the internal core member 4 beinginserted into the partially formed veneer member 5. With the internalcore member 4 so positioned, the remainder of the veneer member 5 may beformed around the internal core member 4 so as to enclose or entrap theinternal core member 4 within a cavity of the veneer member 5. Such anapproach is shown in FIGS. 5A-5D. In FIG. 5A, a lower portion “L” of theveneer member 5 is formed. An intermediate portion “I” of the veneermember 5 may then be formed onto the lower portion “L”, as in FIG. 5B.The intermediate portion “I” is formed so as to define a cavity “C”.With the veneer member 5 in the partially formed condition of FIG. 5B, acorresponding portion of the internal core member 4 is inserted into thecavity “C”, as shown in FIG. 5C. Finally, when the internal core member4 has been properly positioned within the cavity “C”, an upper portion“U” of the veneer member 5 is formed onto the intermediate portion “I”,thus completing the formation of the veneer member 5, as in FIG. 5D.Following formation of the veneer member 5, it may be subjected toadditional processing before being ready for use.

The various portions of the veneer member 5 may be sequentially formedusing any suitable approach, including three-dimensional (“3D”)printing. A 3D-printed object is formed by sequentially forming aplurality of thin layers of material, with each successive layer beingpositioned at least partially above and onto the immediately precedinglayer. Thus, if the veneer member 5 of FIGS. 5A-5D is formed via 3Dprinting, a first lower layer is applied to a platform or printing bed.A second lower layer is applied onto the first lower layer, followed bysubsequent lower layers being applied onto each other until the lowerportion “L” of FIG. 5A has been formed. Next, a first intermediate layeris applied onto the uppermost lower layer (i.e., onto the lower portion“L”), followed by subsequent intermediate layers being applied onto eachother until the intermediate portion “I” of FIG. 5B has been formed.Then, after the internal core member 4 has been inserted into the cavity“C” defined by the intermediate portion “I”, a first upper layer isapplied onto the uppermost intermediate layer (i.e., onto theintermediate portion “I”), followed by subsequent upper layers beingapplied onto each other until the upper portion “U” (and, hence, theveneer member 5) has been completely formed.

The individual layers may be formed by any suitable approach. Forexample, if the veneer member 5 is to be formed of a metallic material,a thin layer of metal powder may be applied to a printing bed andsintered using a laser system. Another layer of metal powder is thenapplied onto the first layer, with the second layer being sintered usingthe laser system. This process is repeated until enough layers of metalpowder have been applied and sintered to form the various portions ofthe veneer member 5, with the process being suspended between formationof the intermediate portion “I” and the upper portion “U” to allow forinsertion of the internal core member 4. Other approaches to forming thevarious layers are described in U.S. Pat. No. 9,937,580 (which describesa method of using a hot-wire, with a laser precisely melting metal at adesired location) and U.S. Pat. No. 10,029,406 (which describes a methodin which feedstock of material is fed onto a fabrication platform andmelted by a high-energy source to form a molten droplet or particle atthe point of contact), both of which are hereby incorporated herein byreference. It should be understood that these approaches are merelyexemplary, and that other approaches may also be employed withoutdeparting from the scope of the present disclosure.

Regardless of how exactly the individual veneer members 5 are formed, itshould be understood that the outer veneer members 5 may be differentlyconfigured from each other, rather than being identical. For example,FIG. 7 shows examples of differently configured outer veneer members 5that may be incorporated into a single elongated member. In theembodiment of FIG. 7 , the outer veneer members 5 are shown as beingprovided in four different configurations: the single proximal end piece8; a plurality of common body elements or plates 9, which are short orplate-like and allow for stacking; the single enlarged body element 10,which is of similar design to the other body elements 9, but longer toindicate the optimal anterior position of the distraction device once inits deployed configuration; and the single distal end piece or nosepiece 11. The proximal and distal end pieces 8 and 11 may be mounted andfixed to the internal core member 4 using any suitable approach, whichmay include the method illustrated in FIGS. 5A-5D, adhesion,pressed-fitting, swaging, welding, or pinning. So affixing the endpieces 8 and 11 to the internal core member 4 effectively traps thecommon and enlarged body elements 9 and 10 between the end pieces 8 and11, without the body elements 9 and 10 having to be secured to theinternal core member 4, which allows the body elements 9 and 10 to moveor articulate with respect to the internal core member 4, as will bedescribed in greater detail. By such a configuration, the internal coremember 4 and outer veneer members 5 combine to form a continuous,semi-rigid hybrid elongated member.

As noted above, the common body elements 9 and the enlarged body element10 may articulate with respect to the internal core member 4 to whichthey are mounted. In one embodiment, which is best seen in FIG. 6B, eachof the body elements 9 and 10 may be formed with a dimple 12 andreceptacle 13 on opposing end faces, with the dimple 12 of one bodyelement 9, 10 being at least partially received by the receptacle 13 ofan adjacent body element 9, 10. Such a configuration allows forengagement and rotation as the hybrid elongated member is flexed andmoved from a generally linear configuration to a generally less linearconfiguration. More particularly, the dimple/receptacle pairs functionlike a swivel, with there being a gap 14 between inner edges 16 ofadjacent body elements 9 and 10 being sufficiently sized so as to notinterfere with the articulation of the body elements 9 and 10 requiredfor the hybrid elongated member to move to a generally annular or closedloop configuration, as in FIGS. 1 and 2 . Indeed, in one embodiment, thebody elements 9 and 10 are configured such that there remains a gap 14between the inner edges 16 of adjacent body elements 9 and 10 when aclosed loop is formed by the distal end piece 11 coming into contactwith a side surface of the proximal end piece 8, as shown in the circledetail 15 of FIG. 2 . In an alternative embodiment, the body elements 9and 10 may be configured such that the inner edges 16 of adjacent bodyelements 9 and 10 do come into contact with each other upon the hybridelongated member moving into its final deployed configuration, whichlimits the amount of flexion that can be accomplished.

The distal ends of the first and second elongated members 1 and 2(whether provided with a hybrid or non-hybrid configuration) can havechamfer or incline or wedge features to ease the passage of theelongated member through tissue, such as bone or vertebral discmaterial. For example, FIG. 2 shows a chamfer or incline feature visibleon the upper surface of the distal end of the first elongated member 1.It should be understood that the lower surface of the distal end of thesecond elongated member 2 may include a similar chamfer feature.

A non-hybrid elongated member of the distraction device may also includefeatures that add flexibility to the elongated member to assist inbending or changing the configuration of the elongated member from agenerally linear configuration to a less linear configuration and viceversa. For example, a non-hybrid elongated member may include lateralteeth and intermediate slots or indents (similar in structure to theinner edges 16 and gaps 14 of the body elements 9 and 10 of a hybridelongated member) that aid in relieving stress and add flexibility tothe elongated member. When the elongated member is deployed in tissue,the slots may also provide gaps for the introduction of bone filler orbone graft materials, cements, or pharmaceutical compounds to thetissues.

Other features may also be added to enhance the functionality of theelongated members, including grooves, slots, channels, and pockets andteeth or other extensions of various shapes. For example, the proximalend of the augmenting elongated member 3 may be provided with a cavity(FIG. 11 ) configured to receive the distal portion of a removable,elongated guide member 25 (FIG. 20 ). The structure and function of theguide member 25 will be described in greater detail herein.

The first and second elongated members 1 and 2 may be provided withformations that assist in maintaining the position of the first andsecond elongated members 1 and 2 while the augmenting elongated member 3is inserted therebetween. As shown in FIG. 27 , an anchoring ortethering system or wires can be used to hold the first and secondelongated members 1 and 2 in place while the augmenting elongated member3 is inserted between the first and second elongated members 1 and 2.The illustrated tethering system includes a pair of anchor wires orcables or filaments, each of which attaches to the proximal end of oneof the first and second elongated members 1 and 2. Each anchor wire mayinclude an enlarged end (e.g., a generally spherical or ball-shaped endpiece) that is at least partially received within a cavity definedwithin the proximal end of the associated elongated member (FIG. 1 ).Such an anchoring system is described in greater detail in U.S. Pat. No.9,480,574.

The first and second elongated members 1 and 2 may also be provided witha slot 6 (FIG. 5 ) extending along all or a portion of their lengths toreceive a complementary raised rib or formation of the augmentingelongated member 3 to prevent separation of the elongated members. Inone embodiment, the slot 6 has a relatively narrow necked-down portionand a wider portion to receive a generally T-shaped raised rib of theaugmenting elongated member 3, as described in greater detail in U.S.Pat. No. 9,480,574. In the case of a hybrid configuration, therelatively narrow necked-down portion of the slot 6 may be defined bythe outer veneer members 5, while a wider portion of the slot 6 may bedefined by the internal core member 4, as in the embodiment of FIG. 5 .

One or more of the elongated members may also be provided with aformation that accommodates a shaping member. For example, FIG. 5 showsan outer veneer member 5 having a through hole or aperture 17 positionedadjacent to the cavity that accommodates the internal core member 4.Although not provided in the embodiment of FIGS. 3-5 , a hybridelongated member may include a shaping member 7 (FIGS. 6A-7 ) receivedin the aligned holes 17 of the outer veneer members 5, as in theembodiment of FIGS. 6A and 6B. A non-hybrid elongated member, such asthe augmenting elongated member of FIGS. 12A and 12B may include asimilarly configured bore or channel configured to receive a shapingmember 22. If provided, the shaping members 7 and 22 are preferablyfixed in place within the associated elongated member according to anyof a number of suitable approaches to prevent the shaping member 7, 22from backing out or otherwise becoming free of the associated elongatedmember.

The shaping member 7, 22 may be configured as an elongated rod formed ofa shape memory material, such as nitinol. The shaping member 7, 22provides the force required to deflect the associated elongated memberfrom its generally linear configuration to a generally less linearconfiguration. FIG. 8 shows a shaping member 7 in a free, unconstrainedstate, which corresponds to the generally annular or closed loopconfiguration that the elongated members may assume in their finaldeployed configurations of FIGS. 1-2 and 11 . The configuration of FIG.8 may be imparted to the shaping member 7, 22 according to aheat-treating process of the type that is well-known to thoseexperienced in working with shape memory materials.

One or more of the elongated members may be provided with a shapingmember. For example, FIGS. 12A and 12B show an embodiment in which onlythe augmenting elongated member 3 includes an associated shaping member22. FIG. 13 shows an embodiment in which each of the elongated membersincludes an associated shaping member 23, while FIG. 14 shows anembodiment in which only the first and second elongated members 1 and 2are provided with associated shaping members 24. It should be understoodthat these illustrated embodiments are merely exemplary and that, inother embodiments, only one of the first and second elongated members 1and 2 may be provided with an associated shaping member (with theaugmenting elongated member 3 and the other elongated member omitting ashaping member) or one of the first and second elongated members 1 and 2and the augmenting elongated member 3 may be provided with associatedshaping members, while the other one of the first and second elongatedmember omits a shaping member. Further, it should be understood thatother aspects of the present disclosure may be embodied in or employedin combination with a distraction device omitting a shaping member.

The number and position of the shaping member or members, if provided,affects the operation of the resulting distraction device. For example,providing a shaping member 22 in only the augmenting elongated member 3(as in FIG. 12 ) could make it simpler to incorporate an anchoringsystem into the first and second elongated members 1 and 2, as notedabove. On the other hand, incorporating a shaping member 13 into each ofthe elongated members (as in FIG. 13 ) would provide a greaterclosing/holding force in a generally annular or closed loopconfiguration compared to an embodiment having fewer than three shapingmembers. Incorporating shaping members 24 into only the first and secondelongated members 1 and 2 (as in FIG. 14 ) may better allow for removaland repositioning of the augmenting elongated member 3, in the eventthat a revision needs to occur during deployment of the distractiondevice.

In an alternative embodiment, the first and/or second elongated member 1and 2 may be provided with an elongated shaping member that extendsproximally out of the proximal end of the elongated member, rather thanbeing fully embedded within the elongated member. By such aconfiguration only the distal portion of the shaping member (i.e., theportion positioned within the associated elongated member) is configuredto automatically move from the generally linear configuration to agenerally less linear configuration, with the remainder of the shapingmember (i.e., the portion extending proximally out of the associatedelongated member) being configured to remain in a generally linearconfiguration. The distal portion of the shaping member would be allowedto automatically move the associated elongated member from the generallylinear configuration to a generally less linear configuration (which maybe its final generally linear configuration), followed by the shapingmember being withdrawn from the associated elongated member upon thedistraction device being fully deployed between the tissue layers. Insuch an embodiment, the augmenting elongated member 3 may be providedwith a fully embedded shaping member 7, as described above, whichremains in the augmenting elongated member 3 following implantation ofthe distraction device.

In another alternative embodiment, rather than a hybrid elongated memberincluding both an internal core member 4 and a shaping member 7, theinternal core member 4 may be at least partially formed of a shapememory material to provide the functionality of the shaping member 7. Itmay be advantageous for such an internal core member 4 to be partiallyformed of a PEEK material or other radiopaque material to allow fordetection and visualization of the internal core member 4 duringimplantation. For example, the internal core member 4 may comprise ashape memory material coated with a PEEK material or other radiopaquematerial to combine the functionality of the previously describedinternal core member 4 and shaping member 7. Additionally, if theinternal core member 4 is at least partially formed of a shape memorymaterial, it may be advantageous for it to be formed with slots or otherformations for enhanced flexibility, as the internal core member 4typically has a greater cross-sectional area than the shaping member 7,which may require such flexibility-enhancing features to allow theinternal core member 4 to move from the generally linear configurationto a final generally less linear configuration.

FIGS. 15-19 illustrate yet another embodiment of a tissue distractiondevice 50 according to the present disclosure, which may be particularlyconfigured for lordotic correction. The embodiment of FIGS. 15-19 issimilar to other embodiments described herein, but includes a number ofdifferences, which may be incorporated into the other embodimentsdescribed herein. For example, FIG. 15 shows the components of an upperelongated member 51 of the tissue distraction device 50 that may becompared to the components of the upper elongated member of FIG. 7 .FIG. 7 shows an upper elongated member comprised of a proximal end piece8, a plurality of common body elements or plates 9, a single enlargedbody element 10, a distal end piece or nose piece 11, an internal coremember 4, and a shaping member 7. In the embodiment of FIGS. 15-19 , anupper elongated member 51 (and/or a lower elongated member 52) iscomprised of a distal end piece 53 (which may be configured similarly tothe distal end piece 11 of FIG. 7 ), a single body piece 54, and amodified proximal end piece 55. While FIG. 15 does not illustrate ashaping member, it should be understood that a shaping member may beincluded without departing from the scope of the present disclosure.

The modified proximal end piece 55 of FIG. 15 may be understood as acombination of the proximal end piece 8 and the internal core member 4of FIG. 7 , with a proximal portion 56 thereof configured similarly tothe proximal end piece 8 of FIG. 7 and a distal portion 57 thereofconfigured similarly to a portion of the internal core member 4 of FIG.7 . By providing a single piece 55 in place of the two pieces of FIG. 7, assembly of the elongated member 51 may be simplified, with the distalportion 57 of the modified proximal end piece 55 (which may be referredto herein as the internal core member) providing a platform onto whichthe body piece 54 and then the distal end piece 53 may be slid in aproximal direction. The distal end piece 53 may be secured to theinternal core member 57 by any suitable approach (e.g., being pinned,screwed, mechanically fastened, or adhered) to trap the body piece 54between the distal end piece 53 and the proximal portion 56 of themodified proximal end piece 55. While FIG. 15 shows the internal coremember 57 monolithically formed with the proximal portion 56, it shouldbe understood that the internal core member 57 may instead beincorporated into the distal end piece 53.

As the internal core member 57 is preferably flexible (to allow for achange in the configuration of the elongated member 51 duringimplantation), the modified proximal end piece 55 is preferably formedof a flexible material, such as PEEK or another polymer, with themodified proximal end piece 55 being manufactured using any of a numberof suitable techniques, including machining or milling techniques. Thus,rather than the proximal portion 56 being formed of a generally rigidmaterial (as is the case with the proximal end piece 8 of FIG. 7 ), theproximal portion 56 is instead formed of a more flexible material.However, while the entire modified proximal end piece 55 may be formedof the same generally flexible material, it should be understood thatthe proximal portion 56 will tend to be less deformable than theinternal core member 57 due to it having a larger cross section.

Turning now to the modified body piece 54, it comprises a plurality ofindividual outer veneer members or body elements 58 a-58 c (collectivelyreferred to as 58) corresponding generally to the common body elementsor plates 9 and enlarged body element 10 of FIG. 7 . Rather than beingseparately formed, at least two of the individual body elements 58 ofthe modified body piece 54 are formed (e.g., by 3D printing or any othersuitable approach) as a single piece, rather than all of the bodyelements 58 being separately formed. In the illustrated embodiment, allof the body elements 58 are formed as a single piece, but it should beunderstood that one or more of the body elements 58 may be separatelyprovided. Each constituent body element 58 of the modified body piece 54may be connected to the adjacent body element 58 by one or morefrangible bridges 59 (FIGS. 16 and 17 ) that are configured to be brokento separate the previously connected body elements 58. In such anembodiment, the single body piece 54 is associated with the internalcore member 57, followed by the internal core member 57 being deformed(e.g., by moving the internal core member 57 from a generally linearconfiguration to an arcuate or annular configuration). So deforming theinternal core member 57 causes the frangible bridges 59 to break, thusseparating the constituent body elements 58 of the body piece 54.Thereafter, the internal core member 57 may be returned to the generallylinear configuration prior to implantation.

While such “single piece” construction may be particularly advantageousfor the body elements, it should be understood that one or both of theend pieces (when the proximal end piece is formed of the same materialas the body elements, as in FIG. 7 ) may be integrally formed with anadjacent body element (i.e., formed as a single piece). In such anembodiment, the single piece incorporating the end piece(s) isassociated with the internal core member (which may include the endpiece(s) being fixedly secured to the internal core member), followed bythe internal core member being deformed to break the frangible bridge(s)of the single piece and separate each of the veneer members prior toimplantation. It should be understood that bridges may be incorporatedinto the manufacture of the veneer members of the other embodimentsdescribed herein and that this aspect of the present disclosure is notlimited to the embodiment of FIGS. 15-19 .

It may be particularly advantageous for the body elements to beconnected together during manufacture if they are differently configuredand arranged in a particular orientation. For example, it will be seenthat the body elements 58 of FIGS. 15-19 do not have a uniform height orthickness, but that at least two of the body elements 58 have differentheights. So providing the body elements 58 with a varying thicknessalong its length will cause different amounts of distraction along thelength of the distraction device 50 (FIG. 19 ). For instance, as bestshown in FIG. 16 , the height or thickness of the body elements 58gradually or incrementally increases from a distal-most body element 58a to a more centrally positioned body element 58 b. The height orthickness of the body elements 58 gradually or incrementally decreasesfrom the more centrally positioned, tallest body element 58 b to aproximal-most body element 58 c. The more distal body elements 58(including the distal-most body element 58 a) may be thinner (shorter)than the more proximal body elements 58 (including the proximal-mostbody element 58 c), which may be thinner (shorter) than more centrallypositioned body elements 58 (including the tallest body element 58 b).In this case, the increase in the height of the proximal portion of thedistraction device 50 will be greater than the augmentation in theheight of the distal portion of the distraction device 50, but less thanthe augmentation in the height of the central portion of the distractiondevice 50.

It should be understood that the illustrated configuration is merelyexemplary and that other configurations (e.g., a configuration in whichthe more distal body elements are the thickest or tallest of the bodyelements) are also within the scope of the present disclosure. Forexample, in addition to (or instead of) body elements having differentheights, it is also within the scope of the present disclosure for twoor more body elements of an elongated member to have different widths,rather than the body elements having the same width (as best shown inFIG. 17 ). It should also be understood that the body elements 58 ofFIGS. 15-19 may have a uniform height or thickness (and/or varyingwidths) and that the body elements of the other embodiments describedherein may having varying heights or thicknesses (and/or varying widths)without departing from the scope of the present disclosure.

The ability to create a greater increase in height in one region of adistraction device allows for adjustments in the curvature of the spineof a patient. For instance, a collapsed disc in the lumbar region of thespine can result in the loss of the normal lordosis in the lumbar regionof the spine. The insertion of upper and/or lower elongated members 51and 52 of variable thickness/height in a collapsed lumbar disc canrestore the lumbar disc to the more normal morphology of a greaterheight on its anterior region as compared to its posterior region. Insuch a situation, the upper and/or lower elongated members 51 and 52 mayhave a greater height at its/their central region between the distal andproximal ends than at either the proximal end or distal end, as in FIGS.18 and 19 . While FIGS. 18 and 19 show upper and lower elongated members51 and 52 configured as mirror images of each other (which may beparticularly advantageous for lordotic correction), with an augmentingelongated member 60 providing substantially uniform separation of thetwo other elongated members 51 and 52, it should be understood that theupper and lower elongated members 51 and 52 may be configured as otherthan mirror images of each other.

According to an exemplary implantation method (which may be employedwith any of the embodiments described herein), an access port is madethrough the annulus of a vertebral disc using instruments and endoscopicor minimally invasive procedures generally known to those skilled in theart. The access port may be relatively small (e.g., no larger than thesize of a deployment cannula used to implant the distraction device),such that the procedure may be minimally invasive, with the resultingtissue distraction height being greater than the height of the accessport. The location of the access port may vary without departing fromthe scope of the present disclosure, but it is preferred for thelocation of the access port be chosen so as to decrease the risk ofnerve damage. In one embodiment, the access port is positioned so as tofacilitate a transforaminal lumbar interbody fusion (“TLIF”) approach,but other approaches may also be practiced without departing from thescope of the present disclosure. For example, according to anotherapproach, the access port may be positioned so as to facilitatedeployment of the elongated members through Karnbin's triangle, which isdefined by the exiting nerve root (the hypotenuse of the triangle), thesuperior border of the inferior vertebra (the base of the triangle), andthe traversing nerve root (the height of the triangle). While thisapproach results in an access port that is positioned at a differentlocation than in the illustrated TLIF approach, it should be understoodthat the method of inserting the elongated members so as to define theimplant in situ may be substantially the same.

Optionally, all or a portion of the nucleus pulposus is removed and theendplates of the adjacent vertebrae are scraped to cause bleeding andpromote the fusion of bone graft material to the vertebral endplates.Sizing paddles or like apparatus, may be slipped through the access portto determine the minimum disc height and the desired final disc height.Based on the minimum and desired final disc height measurement from thesizing paddles, the physician chooses the deployment cannula anddistraction device sizes. The maximum outer dimension of the deploymentcannula used to deliver the distraction device is preferably similar orslightly smaller in height than the minimum disc height measured.Accounting for the cannula wall thickness and any gap between thecannula and the top-to-bottom height of the first and second elongatedmembers 1 and 2, the first and second elongated members 1 and 2 togetherare selected so as to be slightly less in height, top to bottom, thanthe minimum disc height.

FIG. 26 shows an exemplary deployment device 37 that is suitable forsuch a procedure. The deployment device 37 may be configured andfunction according to the description of U.S. Pat. No. 9,480,574.Briefly, the deployment device 37 includes a deployment cannula 46 (FIG.32 ) in which the elongated members are positioned and constrained intoa generally linear configuration, with the first and second elongatedmembers 1 and 2 arranged in a stack distally of the augmenting elongatedmember 3. The first and second elongated members 1 and 2 are advancedout of the deployment cannula and into position between two tissuelayers, such as by operation of a pusher member of the deployment device37 or by distally advancing the guide member 25, which causes theaugmenting elongated member 3 to press against the first and secondelongated members 1 and 2 and advance them out of the deploymentcannula. Advancement of the first and second elongated members 1 and 2optionally includes moving them from their generally linearconfiguration to the generally less linear configuration 43 of FIG. 30 .This movement may be automatic (e.g., if the first and second elongatedmembers 1 and 2 are provided with associated shaping members) or may becontrolled by an operator or surgeon (e.g., by operating pull wires ofthe type described in greater detail in U.S. Pat. No. 9,480,574).

With the first and second elongated members 1 and 2 positioned outsideof the deployment cannula and in the generally less linearconfiguration, the augmenting elongated member 3 may be advanced out ofthe deployment cannula and into place between the first and secondelongated members 1 and 2. FIG. 31 shows the augmenting elongated member3 exiting the deployment cannula, which causes the augmenting elongatedmember 3 to contact and spread apart the first and second elongatedmembers 1 and 2, thereby increasing the dimensional aspect or height ofat least a portion of the distraction device. The degree of heightincrease of the distraction device is dependent upon the height of theaugmenting elongated member 3. For instance, a thicker augmentingelongated member (i.e., an augmenting elongated member having arelatively great height) will cause a greater increase in the height ofthe distraction device than a thinner augmenting elongated member (i.e.,an augmenting elongated member having a relatively small height). Inembodiments inserted into the disc space to distract adjacent vertebralbodies, the height of the distraction device (which is generally equalto the combined heights of the bodies of the constituent elongatedmembers) is preferably sufficient to restore the disc to its normalheight or thereabout, which will depend on the size of the patient andthe disc's location in the spinal column. The height of the distractiondevice can be, for example, from about 5 mm to about 15 mm. Moreparticularly, the height can be from about 7.5 mm to about 13.5 mm, orabout 9 mm to about 12 mm and ranges therein. For relatively shortindividuals or children, the disc size and, consequently, the height ofthe support structure can be, for example, from about 5 mm to about 7mm. For relatively tall individuals, the disc height and, consequently,the height of the support structure can be, for example, from about 9 mmto about 15 mm or greater potentially. In other applications, thedimensions (including the heights) of the individual elongated membersand the resulting distraction device may vary without departing from thescope of the present disclosure.

In one embodiment, the thickness of the augmenting elongated member 3can be different along its length to cause different amounts ofadditional distraction along the length of the distraction device. Forinstance, the proximal portion of the augmenting member 3 may be thicker(taller) than the distal portion of the augmenting member 3, in whichcase the increase in the height of the proximal portion of thedistraction device will be greater than the augmentation in the heightof the distal portion of the device. The ability to create a greaterincrease in height in one region of a distraction device allows foradjustments in the curvature of the spine of a patient. For instance, acollapsed disc in the lumbar region of the spine can result in the lossof the normal lordosis in the lumbar region of the spine. The insertionof an augmenting elongated member 3 of variable thickness/height betweenfirst and second elongated members 1 and 2 deployed in a collapsedlumbar disc can restore the lumbar disc to the more normal morphology ofa greater height on its anterior region as compared to its posteriorregion. In such a situation, the augmenting member 3 may have a greaterheight at its central region between the distal and proximal ends thanat either the proximal end or distal end. Rather than (or in additionto) the augmenting member 3 having a varying thickness, one or both ofthe first and second elongated members 1 and 2 may have a varyingthickness (as in FIGS. 15-19 ), if lordotic correction is required.Alternatively, the elongated members may be configured to combine toform a distraction device having a generally uniform height ordimensional aspect for uniform distraction of a pair of tissue layers.

Preferably, once augmented, the height or dimensional aspect of thedistraction device is fixed and is not adjustable or variable, while theaugmenting member 3 is preferably fixed in position between the firstand second elongated members 1 and 2 and not removable. For example, asdescribed above, the elongated members may be provided with matingformations that prevent the first and second elongated members 1 and 2from separating from the augmenting elongated member 3. Prior to fullinsertion of the augmenting elongated member 3, it may be movedproximally and at least partially out of position between the first andsecond elongated members 1 and 2 for repositioning and readjustment, asnecessary. If the augmenting elongated member 3 is provided with anassociated guide member 25, the guide member 25 may be moved proximallyto withdraw the augmenting elongated member 3 from between the first andsecond elongated members 1 and 2.

FIG. 31 shows the augmenting elongated member 3 in a partially insertedcondition 44, while FIG. 32 shows the augmenting elongated member 3 in afully inserted condition 45. As shown in FIG. 32 , the augmentingelongated member 3 may be shorter or less elongated than the first andsecond elongated members 1 and 2, thereby defining a window in the fullyassembled distraction device. The function of the window will bedescribed in greater detail herein.

FIGS. 27-29 illustrate insertion of the distraction device using amodified deployment cannula 38. In particular, the deployment cannula 38includes a deformable distal end, which is configured to change betweenan initial configuration (generally identified in FIG. 28 at 40) and anexpanded or deformed configuration (generally identified in FIG. 29 at41). In the illustrated embodiment, the distal end of the deploymentcannula 38 has a split design or configuration, which allows a first orupper portion of the distal end of the deployment cannula 38 toresiliently flex away from a second or lower portion of the distal endof the deployment cannula 38. The distal end of the deployment cannula38 retains its initial configuration with the first and second elongatedmembers 1 and 2 partially advanced out of the deployment cannula 38 (asgenerally identified in FIG. 28 at 39), before moving to its deformedconfiguration when the augmenting elongated member 3 is at leastpartially inserted between the first and second elongated members 1 and2 with the first and second elongated members 1 and 2 still partiallypositioned within the deployment cannula 38 (as generally identified inFIG. 29 at 42). FIGS. 28 and 29 show the elongated members retainingtheir generally linear configuration (which would be the case for anembodiment in which shaping members are omitted and replaced with someother shaping mechanism, such as pull wires), but it should beunderstood that the portions of the first and second elongated members 1and 2 positioned outside of the deployment cannula 38 will typicallymove from their generally linear configuration to a generally lesslinear configuration upon exiting the deployment cannula 38.

Rather than the opposing portions of the distal end of the deploymentcannula 38 freely pivoting away from each other, they are preferablydeformed outwardly against a resilient force that tends to bring theopposing portions back to their initial configuration. Such a resilientforce helps to maintain proper position of the elongated members duringassembly of the distraction device and ensure that the augmentingelongated member 3 is successfully engaged by the first and secondelongated member 1 and 2 during insertion. However, while theillustrated configuration may be preferred, it should be understood thatthe deformability of the distal end of the deployment cannula may beimparted by a different mechanism without departing from the scope ofthe present disclosure. It should also be understood that a deploymentcannula with a deformable distal end may be used in combination with anysuitable distraction device and is not limited to use in combinationwith the distraction devices described herein.

As described above, the augmenting elongated member 3 may be providedwith an associated guide member 25, with the combined augmentingelongated member and guide member being generally identified at 26 inFIG. 20 . FIGS. 21-25 illustrate an exemplary method in which the guidemember 25 is used to inject a filler material into an interior of adeployed distraction device, followed by removal of the guide member 25from the distraction device. In particular, the distraction device isformed with the guide member 25 attached to the augmenting elongatedmember 3, with at least a portion of the guide member 25 remainingwithin the deployment cannula during implantation. Once the deploymentis completed, the deployment device (identified in FIG. 21 at 27 in acondition in which a pusher member has been advanced to deploy theelongated members) is disconnected from the distraction device 28(including the guide member 25) and moved proximally (as indicated at 29in FIG. 21 ) to completely dissociate the deployment device from thedistraction device 28.

The guide member 25 serves as a guide for an injection aid 30, which isshown in FIG. 22 . The injection aid 30 includes a follower member orguiding tube 33 and a funnel member or guide port 32. The followermember 33 is associable with the guide member 25 to allow movement ofthe injection aid 30 along at least a portion of the length of the guidemember 25. For example, the follower member 33 may be configured as atube that receives the guide member 25 for sliding movement of theinjection aid 30 along the guide member 25 toward and away from thedistraction device 28. As for the funnel member 32, it defines a lumenand extends between a proximal end or funnel 31 configured toaccommodate at least a portion of an injection device 34 (FIG. 23 ) anda distal end. In addition to allowing for movement of the injection aid30 along the guide member 25, the follower member 33 also serves toalign the distal end of the funnel member 32 with a window defined inthe distraction device 28. To that end, it may be advantageous for thefollower member 33 to be configured to have a keyed relationship withthe guide member 25, such that the follower member 33 may only beassociated with the guide member 25 in one orientation that properlyaligns the funnel member 32 and the window.

The injection aid 30 is moved along the guide member 25 to place thedistal end of the funnel member 32 adjacent to the window of thedistraction device 28, at least partially inside of the window, or inthe interior of the distraction device 28 via the window. With thedistal end of the funnel member 32 so positioned, an injector device 34(which, in one embodiment, is configured as described in U.S. PatentApplication Publication No. 2016/0228261, which is hereby incorporatedherein by reference) is partially advanced into the lumen of the funnelmember 32. The injector device 34 is then used to introduce a fillermaterial or bone graft material into the interior of the distractiondevice 28.

Upon completion of that step, the injector device 34 and injection aid30 may be moved proximally away from the distraction device 28 tocompletely dissociate the injection aid 30 and the injector device 34from the distraction device 28 and the guide member 25. The guide member25 may then be removed from the distraction device 28. In oneembodiment, a proximal portion of the guide member 25 includes aformation or recess 36 (FIG. 20 ) configured to accommodate a handlemember 35, as shown in FIG. 24 . With the handle member 35 attached tothe guide member 25, the handle member 35 may be manipulated (e.g., tocause the guide member 25 to rotate about its central axis) todisconnect the guide member 25 from the distraction device 28, leavingonly the distraction device 28 between the tissue layers (FIG. 25 ) tocomplete the implant deployment operation. It should be understood thatthe guide member 25 and associated method of use may be used incombination with other distraction members having an interior to be atleast partially filled with a filler material and is not limited to usein combination with distraction devices of the type described herein.

Following removal of the guide member 25, the access port may be closed,along with any other access points opened to reach the disc space.Additional details of a suitable implantation method may be found inU.S. Pat. No. 9,480,574.

It will be understood that the embodiments described above areillustrative of some of the applications of the principles of thepresent subject matter. Numerous modifications may be made by thoseskilled in the art without departing from the spirit and scope of theclaimed subject matter, including those combinations of features thatare individually disclosed or claimed herein. For these reasons, thescope hereof is not limited to the above description but is as set forthin the following claims, and it is understood that claims may bedirected to the features hereof, including as combinations of featuresthat are individually disclosed or claimed herein.

The invention claimed is:
 1. A tissue distraction device comprising: afirst elongated member and a second elongated member, an augmentingelongated member configured to cooperatively interact with the firstelongated member and the second elongated member to increase adimensional aspect of the tissue distraction device, wherein each of thefirst elongated member and the second elongated member comprises ahybrid structure comprised of an elongated internal core member and aveneer at least partially surrounding the elongated internal core memberand spaced along the length of the elongated internal core member,wherein the elongated internal core member and the veneer comprisedifferent materials, wherein the elongated internal core member issufficiently flexible to change between a generally linear configurationand a generally less linear configuration, wherein the elongatedinternal core member comprises a polymer material, and the veneer issubstantially formed of a generally rigid material, wherein the veneercomprises a metallic material.
 2. The tissue distraction device of claim1, wherein the elongated internal core member is substantially formed ofpolyetheretherketone.
 3. The tissue distraction device of claim 1,wherein said generally rigid material comprises a titanium material. 4.The tissue distraction device of claim 1, wherein at least a portion ofan outer surface of the veneer has a rough, porous surface.
 5. Thetissue distraction device of claim 1, wherein the first elongated memberand the second elongated member are configured to be in a generallyannular configuration when the elongated internal core members are insaid generally less linear configuration.
 6. The tissue distractiondevice of claim 1, further comprising a shaping member, wherein theshaping member is configured to automatically move the tissuedistraction device from the generally linear configuration to thegenerally less linear configuration.
 7. The tissue distraction device ofclaim 6, wherein the shaping member is fully embedded within theaugmenting elongated member.
 8. The tissue distraction device of claim1, wherein the augmenting elongated member comprises a shape memorymaterial and is configured to move the tissue distraction device fromthe generally linear configuration to the generally less linearconfiguration.
 9. The tissue distraction device of claim 1, wherein thesecond elongated member is a mirror image of the first elongated member.10. The tissue distraction device of claim 1, wherein the firstelongated member comprises an inclined surface on an upper surface of adistal end to ease passage of the first elongated member through tissue.11. The tissue distraction device of claim 10, wherein the secondelongated member comprises an inclined surface on a lower surface of adistal end to ease passage of the second elongated member throughtissue.
 12. The tissue distraction device of claim 1, wherein the firstelongated member and the second elongated member comprise a slotextending along a portion of their lengths to receive a raised rib ofthe augmenting elongated member.
 13. The tissue distraction device ofclaim 1, wherein the first elongated member and the second elongatedmember comprise a slot with a relatively narrow necked-down portion toreceive a T-shaped raised rib of the augmenting elongated member. 14.The tissue distraction device of claim 1, further comprising a shapememory rod configured to deflect the augmenting elongated member. 15.The tissue distraction device of claim 14, wherein the shape memory rodremains in the augmenting elongated member following implantation of thetissue distraction device.
 16. The tissue distraction device of claim 1,wherein the veneer extends along at least a portion of an upper surfaceand lateral surfaces of the first elongated member.
 17. The tissuedistraction device of claim 16, wherein the veneer extends along atleast a portion of a lower surface and lateral surfaces of the secondelongated member.
 18. The tissue distraction device of claim 1, whereinthe augmenting elongated member is configured to be at least partiallyinserted between the first elongated member and the second elongatedmember.
 19. The tissue distraction device of claim 6, wherein theaugmenting elongated member comprises the shaping member.
 20. The tissuedistraction device of claim 1, wherein the augmenting elongated memberis shorter or less elongated than the first elongated member.
 21. Thetissue distraction device of claim 20, wherein the augmenting elongatedmember is shorter or less elongated than the second elongated member.